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About 1.5 million Americans have lupus (systemic lupus erythematosus, or SLE), the most common form), according to the Lupus Foundation of America. The majority, 90%, are women, who usually develop the disease between ages 15 and 44. African-American, Hispanic, and Asian women have a higher risk. Eliza Chakravarty, MD, assistant professor of medicine in the division of immunology and rheumatology at Stanford University School of Medicine, sheds light on a disease you might not know much about.

How do you know if you have lupus?

A lot of people who come to see me have “tested positive for lupus,” meaning they have a positive ANA (antinuclear antibody) test. That doesn't necessarily mean they have lupus or will ever get it. To make a positive diagnosis, you typically will have a positive ANA, but you must have more things happening, such as swelling of the joints, very particular kinds of rashes, evidence that there's something going on in your kidneys, or inflammation in different parts of your body.

A lot of lupus is not really that visible, so you can have lupus and look completely healthy. The other tricky thing is that people often have symptoms like tiredness, fatigue, and achiness, and it's hard to tell whether that's due to the lupus itself because such symptoms are common in a lot of people.

How do you get the disease?

We have no idea. It's an autoimmune disease, which means your immune system, which is made to protect you from viruses and bacteria and other infections, has gotten confused and has recognized parts of your own body as foreign and tries to attack them. We think people probably inherit a susceptibility for getting lupus, but it's not a single gene; it's probably a combination of different genes. In addition, we think something else has to happen that triggers the disease.

Does lupus get progressively worse?

Not necessarily. It can behave so differently in different people. It can be very mild in somebody forever -- only a few rashes and some joint pain here and there. On the other end of the spectrum, it can be a very devastating disease and cause seizures and kidney failure. Most of the time people with lupus live relatively normal lives. The disease certainly can be fatal in some people, but that's a very small proportion.

What about pregnancy if you have lupus?

If you're interested in becoming pregnant, it's a good idea to talk with your doctor to make sure your lupus is under control and the medicines you're taking are not ones that can cause birth defects. There's probably a very small subset, maybe 5% of women, who would be at high risk for having a lot of pregnancy complications. But the majority of women who want to have children can -- and can have healthy pregnancies.

What's ahead for people with lupus?

Now is a very exciting time because we're learning more and more about the disease every day, with the specific goal of trying to understand what causes it so we can try to prevent it as well as [develop] better and safer ways of treating it. These days, we have much better therapies than we had even 20 years ago.